North, west, and south of the highest Teton peaks the soaring spires and
knife-edge ridges of Precambrian rock give way to rounded spurs and
lower flat-topped summits, whose slopes are palisaded by continuous gray
cliffs that resemble the battlements of some ancient and long-abandoned
fortress (fig. 31). As mentioned previously, the cliffs are the
projecting edges of layers of sedimentary rocks of Paleozoic age that
accumulated in or along the margins of shallow seas. At one time the
layers formed a thick unbroken, nearly horizontal blanket across the
Precambrian basement rocks, but subsequent uplift of the eastern edge of
the Teton fault block tilted them westward. They were then stripped from
the highest peaks.
The Paleozoic and younger sedimentary rocks in the Teton region are
subdivided into _formations_, each of which is named. A formation is
composed of rock layers which, because of their similar physical
characteristics, can be distinguished from overlying and underlying
layers. They must be thick enough to be shown on a geologic map. Table 2
lists the various Paleozoic formations present in and adjacent to Grand
Teton National Park and gives their thicknesses and characteristics.
These sedimentary rocks are of special interest, for they not only
record an important chapter of geologic history but elsewhere in the
region they contain petroleum and other mineral deposits.
The Paleozoic rocks can be viewed close at hand from the top of the
Teton Village tram (fig. 32) on the south boundary of the park. A less
accessible but equally spectacular exposure of Paleozoic rocks is in
Alaska Basin, along the west margin of the park, where they are stacked
like even layers in a gigantic cake (fig. 33).